Power Tool Drop Arm with Offset Ribbing

ABSTRACT

A power tool assembly includes a drop arm frame with an opening configured to rotatably support an arbor shaft, a lower surface spaced apart from the opening, and a plurality of ribs extending between the lower surface and the opening. The plurality of ribs define a respective one of a plurality of axes, the plurality of axes intersect at a locus, and the locus is adjacent to, but spaced apart from, a center of gravity of the drop arm assembly. The power tool assembly further includes an actuating device configured to transfer a force to the drop arm assembly when the drop arm assembly is at the first drop arm assembly position, and a control system configured to control the actuating device to transfer the force to the drop arm assembly when an unsafe condition is sensed.

This application claims priority to U.S. Provisional Application Ser.No. 62/132,004 entitled “TABLE SAW WITH DROPPING BLADE”, filed Mar. 12,2015, and U.S. Provisional Application Ser. No. 62/131,977 entitled“SYSTEM AND METHOD FOR CONTROL OF A DROP ARM IN A TABLE SAW”, filed Mar.12, 2015, the disclosures of which are each incorporated herein byreference in their entirety.

FIELD

The disclosure relates to power tools and more particularly to powertools with exposed shaping devices.

BACKGROUND

A number of power tools have been produced to facilitate forming aworkpiece into a desired shape. One such power tool is a table saw. Awide range of table saws are available for a variety of uses. Some tablesaws such a cabinet table saws are very heavy and relatively immobile.Other table saws, sometimes referred to as jobsite table saws, arerelatively light. Jobsite table saws are thus portable so that a workercan position the table saw at a job site. Some accuracy is typicallysacrificed in making a table saw sufficiently light to be mobile. Theconvenience of locating a table saw at a job site, however, makesjobsite table saws very desirable in applications such as generalconstruction projects.

All table saws, including cabinet table saws and jobsite table saws,present a safety concern because the saw blade of the table saw istypically very sharp and moving at a high rate of speed. Accordingly,severe injury such as severed digits and deep lacerations can occuralmost instantaneously. A number of different safety systems have beendeveloped for table saws in response to the dangers inherent in anexposed blade moving at high speed. One such safety system is a bladeguard. Blade guards movably enclose the saw blade, thereby providing aphysical barrier that must be moved before the rotating blade isexposed. While blade guards are effective to prevent some injuries, theblade guards can be removed by a user either for convenience of usingthe table saw or because the blade guard is not compatible for use witha particular shaping device. By way of example, a blade guard istypically not compatible with a dado blade and must typically be removedwhen performing non-through cuts.

Table saw safety systems have also been developed which are intended tobrake the blade when a user's hand approaches or touches the blade.Various braking devices have been developed including braking deviceswhich are physically inserted into the teeth of the blade. Uponactuation of this type of braking device, however, the blade istypically ruined because of the braking member. Additionally, thebraking member is typically destroyed. Accordingly, each time the safetydevice is actuated significant resources must be expended to replace theblade and the braking member. Another shortcoming of this type of safetydevice is that the shaping device must be toothed. Moreover, if a spareblade and braking member are not on hand, a user must travel to a storeto obtain replacements. Thus, this type of safety system can beexpensive and inconvenient.

Another type of table saw uses a safety control system which, inresponse to a sensed unsafe condition, moves a blade beneath the levelof the table. One such system is disclosed in U.S. Pat. No. 8,286,537which issued on Oct. 16, 2012. The '537 patent discloses a power toolincluding a workpiece support surface, a swing arm assembly movablealong a swing path between a first swing arm position whereat a portionof a shaping device supported by the swing arm assembly extends abovethe workpiece support surface and a second swing arm position whereatthe portion of the shaping device does not extend above the workpiecesupport surface, and a latch pin movable between a first positionwhereat the latch pin is engaged with the swing arm assembly and asecond position whereat the latch is not engaged with the swing armassembly.

In general, the power tool in the '537 patent operates in a known manneruntil an unsafe condition is sensed by the safety control system. Inresponse to the sensed unsafe condition, the safety control systemcontrols a pressure operated actuator to force the latch pin from thefirst position to the second position and to force the swing armassembly away from the first swing arm position and toward the secondswing arm position.

The above described safety control systems are effective in reducing thepotential for an unsafe condition. One shortcoming, however, is thatextreme amounts of force are typically used to provide the desiredacceleration of the swing arm. In order to absorb or transfer theextreme force, the components are typically oversized or made from heavymaterials. Such approaches defeat the objectives of providing a compact,lightweight device.

In view of the foregoing, it would be advantageous to provide a powertool with a drop arm assembly which incorporates lightweight materialwhile allowing for high levels of force to be used.

SUMMARY

In one embodiment, a power tool assembly includes a drop arm assemblymovable along a drop path between a first drop arm assembly positionwhereat a portion of a shaping device supported by the drop arm assemblyextends above a workpiece support surface and a second drop arm assemblyposition whereat the portion of the shaping device does not extend abovethe workpiece support surface, the drop arm assembly including a droparm frame with an opening configured to rotatably support an arborshaft, a lower surface spaced apart from the opening, and a plurality ofribs extending between the lower surface and the opening. The pluralityof ribs define a respective one of a plurality of axes, the plurality ofaxes intersect at a locus, and the locus is adjacent to, but spacedapart from, a center of gravity of the drop arm assembly. The power toolassembly further includes an actuating device configured to transfer aforce to the drop arm assembly when the drop arm assembly is at thefirst drop arm assembly position, and a control system configured tocontrol the actuating device to transfer the force to the drop armassembly when an unsafe condition is sensed.

In one or more embodiments, the drop arm assembly moves within a dropplane as it moves along the drop path, the center of gravity is at leastin proximity to the drop plane, and the drop arm frame includessemi-spherical strike pin located in the strike plane.

In one or more embodiments, the drop arm frame is formed substantiallyfrom aluminum, and the drop arm assembly further includes at least onehardened steel pin extending from the drop arm frame, and the power toolassembly includes an alignment housing configured to receive the atleast one hardened steel pin thereby aligning the semi-spherical strikepin with the actuating device.

In one or more embodiments, the drop arm frame includes a pair of spacedapart brackets, each bracket including a respective inner bearing wall,an orbit shaft fixedly mounted to a height adjust carriage, a firstbearing positioned about the orbit shaft and against a first of therespective inner bearing walls, a second bearing positioned about theorbit shaft and against a second of the respective inner bearing walls,an orbit bolt threadedly engaging the orbit shaft, and the orbit shaftand the orbit bolt are configured to compresses the first and secondbearings against the respective inner bearing walls.

In one or more embodiments, the power tool assembly includes a stop padmounted to the lower surface.

In one or more embodiments, the stop pad is positioned directlyoutwardly of at least two of the plurality of ribs.

In one or more embodiments, the plurality of ribs includes at least fourribs.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of thedisclosure and together with a description serve to explain theprinciples of the disclosure.

FIG. 1 depicts a top perspective view of a table saw mounted to awheeled stand;

FIG. 2 depicts a side plan view of the right side of the table saw ofFIG. 1 with the housing, bevel plate, and workpiece support surfaceremoved and the height adjust carriage at an upper position;

FIG. 3 depicts a side plan view of the left side of the table saw ofFIG. 1 with the housing, workpiece support surface, and bevel plateremoved;

FIG. 4 depicts a top perspective view of the height adjust carriage,drop arm assembly, and motor assembly of the table saw of FIG. 1;

FIG. 5 depicts a top perspective view of the height adjust carriage ofFIG. 4 along with rods and tubes used to guide movement of the heightadjust carriage;

FIG. 6 depicts a side cross-sectional view of the motor assembly of FIG.4;

FIG. 7 depicts a plan view of the motor assembly of FIG. 4 from the leftside of the table saw;

FIG. 8 depicts a plan view of the motor assembly of FIG. 4 from the leftside of the table saw after the motor assembly has been rotated toprovide a desired tension to the belt of FIG. 4;

FIG. 9 depicts a side plan view of the orbit portion of the heightadjust carriage of FIG. 4;

FIG. 10 depicts an exploded view of the orbit portion of FIG. 9;

FIG. 11 depicts a partially exploded view of the exemplary embodiment ofan orbit portion;

FIG. 12 depicts a top perspective view of another exemplary embodimentof an orbit bracket;

FIG. 12A depicts a top plan view of the orbit bracket of FIG. 12;

FIG. 13 depicts cross-sectional view of the orbit assembly of FIG. 10supporting the drop arm assembly;

FIG. 14 depicts a bottom perspective cross-sectional view of the orbitassembly of FIG. 13;

FIG. 15A depicts an exploded view of the drop arm assembly of FIG. 4;

FIG. 15B depicts a side perspective view of the drop arm assembly ofFIG. 4;

FIG. 15C depicts a side plan view of the drop arm assembly of FIG. 4;

FIG. 16 depicts a side plan view of the right side of the table saw ofFIG. 1 with the housing and workpiece support surface removed;

FIG. 17 depicts a perspective view of the height adjust carriage of FIG.4 with the pyrotechnic assembly and latch assembly mounted to the heightadjust carriage;

FIG. 18 depicts a perspective view of the cartridge of FIG. 17;

FIGS. 19 and 20 depict perspective views of the pyrotechnic housing ofFIG. 17;

FIG. 21 depicts a partial top plan view of the table taw of FIG. 1 withthe throat plate removed;

FIG. 22 depicts a side cross-section view of the drop arm frame of FIG.4 showing a common point shared by the center of gravity and the locusof the ribs of the drop arm frame;

FIG. 23 depicts a side perspective view of the pyrotechnic housingmounted to the height adjust carriage;

FIG. 24 depicts an exploded view of the pyrotechnic assembly of FIG. 17;

FIG. 25 depicts a top plan view of the active shot of FIG. 17 with anelectrical connector;

FIGS. 26-29 depict the active shot of FIG. 17 moving the latch assemblyof FIG. 17 as the reaction plug of FIG. 24 is threaded into thepyrotechnic housing;

FIGS. 30-31 depict the latch assembly of FIG. 17 biasing the active shotoutwardly from the pyrotechnic housing when the reaction plug isremoved;

FIG. 32 depicts a side plan view of the drop arm assembly of FIG. 4indicating the axes of the various components;

FIG. 33 depicts a side plan view of the table saw of FIG. 1 after thedrop arm assembly has been dropped against a surface while the heightadjust carriage is at an upper position;

FIG. 34 depicts a side plan view of the table saw of FIG. 1 with thedrop arm assembly latched and the height adjust carriage at a lowerposition;

FIG. 35 depicts a side plan view of the table saw of FIG. 1 after thedrop arm assembly has been dropped against a surface with the heightadjust carriage at a lower position;

FIG. 36 depicts a top perspective view of the bounce back latch assemblymounted to the height adjust carriage;

FIGS. 37-39 depict left, top and right plan views of the height adjustcarriage showing ribbing to provide increased strength;

FIGS. 40-41 depict perspective views of the bevel carriage showingribbing to provide increased strength;

FIG. 42 depicts a saw control unit assembly mounted to the bevelcarriage;

FIG. 43 depicts an exploded view of the saw control unit assembly ofFIG. 42 and the bevel carriage;

FIG. 44 depicts an exploded view of the saw control unit assembly ofFIG. 42, the drop arm assembly, and the bevel carriage;

FIG. 45 depicts a side perspective view of the bevel carriage showingcoaxial wiring used to provide communication with various components;

FIG. 46 depicts the shield and center conductor of the coaxial wiringused to provide electrical communication with various components;

FIG. 47 depicts a perspective view of the connection between the centralconductor and the CCP;

FIG. 48 depicts a perspective view of the coaxial wiring offset from itsnormal position whereat it is connected to the bevel carriage with theprotective covering removed to show the exposed shield which connects tothe bevel carriage;

FIGS. 49-50 depict protective coverings used to cover stripped portionsof the coaxial wire and also to provide communication between thecoaxial wire and other components;

FIG. 51 depicts a side perspective view of the table saw of FIG. 1 withthe housing removed to show how components are in communication with theshield of the coaxial wiring;

FIG. 52 depicts an exploded view of the trunnions used to pivot thebevel carriage showing electrical isolation between the workpiecesupport surface and the bevel carriage;

FIG. 53 is a cross-sectional view of the arbor shaft showing electricalisolation of the arbor shaft from the rest of the drop arm assembly andthe belt;

FIG. 54 is an exploded view of the pulley of FIG. 53 which provideselectrical isolation between the belt and the arbor shaft;

FIG. 54A is a side plan view of the outer shell of FIG. 54 showingdovetail splines;

FIG. 55 depicts a perspective view of the motor assembly showingradially directed vents which direct carbon dust away from one or moreof the components;

FIG. 56 depicts a partial exploded view of the throat plate andworkpiece support surface of FIG. 1;

FIG. 57 depicts a perspective view of the throat plate engaged by a knobwith the workpiece support surface removed;

FIG. 58 depicts a top perspective view of the knob of FIG. 56;

FIG. 59 depicts a side plan view of the front of the throat plate;

FIG. 60 depicts a partial perspective view of the drop arm assembly withthe arbor lock of FIG. 15B engaging the pyrotechnic housing to maintainthe drop arm assembly in a latched condition;

FIG. 61 depicts a partial top perspective view of the table saw of FIG.1 with the throat plate removed to allow resetting of the drop armassembly;

FIG. 62 depicts a side perspective view of the HMI unit of FIG. 1;

FIG. 63 depicts an exploded view of the internal components of the HMIunit of FIG. 62;

FIG. 64 depicts a rear plan view of the table saw of FIG. 1 with thebevel carriage at zero degrees;

FIG. 65 depict a rear plan view of the table saw of FIG. 1 with thebevel carriage at forty-five degrees of bevel such that a USB port ofthe saw control unit assembly is visible through a dust port access slotof the table saw housing; and

FIGS. 66-67 depict protective covers which can be used to protect theUSB port of FIG. 65 from undesired access.

Corresponding reference characters indicate corresponding partsthroughout the several views. Like reference characters indicate likeparts throughout the several views.

DETAIL DESCRIPTION OF THE DISCLOSURE

While the power tools described herein are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will herein bedescribed in detail. It should be understood, however, that there is nointent to limit the power tools to the particular forms disclosed. Onthe contrary, the intention is to cover all modifications, equivalents,and alternatives falling within the spirit and scope of the disclosureas defined by the appended claims.

Referring to FIG. 1, a table saw assembly 100 is shown. The table sawassembly 100 includes a table saw 102 mounted to a wheeled stand 104 Thetable saw 102 includes a base housing 106 and a workpiece supportsurface 108. Support surface extensions 110 and 112 are provided toassist in supporting larger workpieces. A fence 114 is provided to guidea workpiece along the workpiece support surface 108.

A riving knife or splitter 116 is positioned adjacent to a shapingdevice which in this embodiment is a blade 118 which extends from withinthe base housing 106 to above the workpiece support surface 108. A bladeguard 120 and kick-back pawls 117 may be attached to the splitter 116.The blade 118 extends through a slot in a throat plate 122. A humanmachine interface (HMI) unit 124 is provided at a front portion of thetable saw 102.

An angle indicator 130 located adjacent to the HMI unit 124 indicatesthe angle of the blade 118 with respect to the workpiece support surface108. A bevel adjust lock 132 may be used to establish the angle of theblade 118 with respect to the workpiece support surface 108 by pivotinga bevel carriage 134 (shown in FIG. 2) within the base housing 106. Thebevel carriage 134 is then clamped between the bevel adjust lock 132 anda bevel clamp 133 (see FIG. 3). As further depicted in FIG. 3, a heightadjust wheel 136 is used to adjust the height of the blade 118 above theworkpiece support surface 108 (not shown in FIG. 3). Rotation of theheight adjust wheel 136 rotates a bevel gear 138 which is engaged with athreaded rod 140. The threaded rod 140 is thus forced to rotate eitherclockwise or counterclockwise, depending upon the direction in which theheight adjust wheel 136 is rotated.

The threaded rod 140 threadedly engages a height adjust carriage 142. Inone embodiment, the threaded rod 140 engages a threaded bushing 152 ofthe height adjust carriage 142. The height adjust carriage 142 is thusforced to move upwardly and downwardly as the threaded rod 140 rotates.Rotation of the height adjust carriage 142 is precluded by a heightadjust rod 144 and a height adjust tube 146 which are fixedly attachedto the bevel carriage 134. The height adjust rod 144 and a height adjusttube 146 extend through openings 148 and 150, respectively, in theheight adjust carriage 142 which are shown in FIG. 4.

In order to reduce the weight of the table saw 102, light-weightmaterials, e.g., aluminum, are used in the manufacture of the heightadjust carriage 142. While effective for reducing weight, aluminum isnot typically strong enough to withstand the various forces (describedmore fully below) which are applied to the height adjust carriage 142without deformation or damage. Accordingly, a powder metallurgy bushing153 shown more clearly in FIG. 5 is provided within the opening 150. Thebushing 153 distributes forces equally along the opening 150, therebyreducing the possibility of damage particularly at the mouth of theopening 150 which could lead to undesired “looseness” between the heightadjust carriage 142 and the height adjust tube 146.

Similarly, a powder metallurgy slotted bushing 154 is provided at theupper mouth of the opening 148 to protect the opening 148 from damagefrom the height adjust rod 144. In other embodiments, one or more of thebushings 153/154 are replaced with a linear bearing or split guide pads.In some embodiments, the bevel carriage 134 is protected by theincorporation of dampening bushings at the locations which support theheight adjust rod 144 and/or the height adjust tube 146.

Returning to FIG. 4, a motor assembly 160 is supported by the heightadjust carriage 142. The motor assembly 160 drives a belt 162, which inone embodiment is made from a conductive material, through an offsetdrive shaft 164 and pulley 166 shown more clearly in FIG. 6. The offsetdrive shaft 164 is offset from a power shaft 168 by a gear 170. Themotor assembly 160 is attached to the height adjust carriage 142 in amanner which allows the belt 162 to be tensioned without the need of alinear tensioner as explained with reference to FIG. 7.

As shown in FIG. 7, the motor assembly 160 is attached to the heightadjust carriage 142 with four screws 172 which are inserted throughrespective mounting slots 174 in a motor gear housing 176. The mountingslots 174 are oriented to define a motor mounting axis of rotation 178which is beneath the axis of rotation 180 of the power shaft 168 whichis in turn below the offset shaft 164. Accordingly, rotation in onedirection of a jack screw 182 which is threadedly engaged with a plate184 fixedly attached to the height adjust carriage 142 causes the jackscrew 182 to push against a plate 186 attached to the motor gear housing176. In one embodiment, the plate 184 is either formed as a portion ofthe height adjust carriage 142 or integrated into the height adjustcarriage 142 as a single unit. Thus, the jack screw 182 is threadedlyengaged with the height adjust carriage 142 instead. Since the plate 186which is impinged by the jack screw 182 is located above the motormounting axis of rotation 178, the motor assembly 160 rotates in thedirection of the arrow 188 from the position of FIG. 7 to the positionof FIG. 8.

Returning to FIG. 4, the above described movement of the motor assembly160 causes the pulley 166 which is attached to the offset drive shaft164 to move in the direction of the arrow 190 away from a slave pulley192 which is rotatably supported by a drop arm assembly 194.Consequently, the belt 162 is placed into tension. Accordingly, themotor assembly 160 can be placed in the position of FIG. 7 for initialassembly, and then pivoted toward the position depicted in FIG. 8 to alocation which provides the desired tension of the belt 162. Thisconfiguration requires less linear travel than a linear adjustmentmechanism to achieve the same tension within a constrained space. Inother embodiments, a spring loaded actuator replaces the jack screw 182to maintain belt tension over time.

Tension of the belt 162 is verified using a belt tension meter insertedthrough a belt tension access port 196 (see FIG. 4) in an upper surfaceof a belt protective cover 198. Positioning of the access port 196 onthe upper surface of the belt protective cover 198 allows for access tothe belt 162 from above the table saw 102. This allows for easier accessto setting the tension of the belt while maintaining structuralrequirements for the height adjustment carriage without flipping the sawupside down to gain access to the belt 162. While depicted as a circularopening, the access port 196 in other embodiments is in a differentgeometry and in certain embodiments is provided with a removable plug oran access door.

Continuing with FIG. 4, the drop arm assembly 194 is movably connectedto the height adjust carriage 142 by an orbit shaft 200 which defines adrop arm orbit axis 201. The location of the drop arm orbit axis 201 iscontrolled to be located between the axis of rotation 202 of the offsetdrive shaft 164 (see FIG. 6), which is also the axis of rotation of thepulley 166, and an axis of rotation 183 of the slave pulley 192 using anorbit bracket 203 further described with reference to FIGS. 9-10.

The orbit bracket 203 includes an orbit shaft hole 204 through which theorbit shaft 200 is inserted. The orbit bracket 203 further includes analignment bore 205 and an anti-rotation slot 206 which receive a locatorpin 207 and anti-rotation pin 208, respectively, which extend from theheight adjust carriage 142. The orbit bracket 203 is connected to theheight adjust carriage 142 by two screws 210.

The axis 211 of the anti-rotation slot 206 is aligned to intersect thecentral axis 212 of the alignment bore 205. Accordingly, when thelocator pin 207 and the anti-rotation pin 208 are positioned within thealignment bore 205 and the anti-rotation slot 206, respectively, theanti-rotation pin 208 and the anti-rotation slot 206 provide an accurateangular position for aligning the drop arm orbit axis 201.

The incorporation of the orbit bracket 203 with the anti-rotation slot206 and the anti-rotation pin 208 enable the use of lightweightmaterials while providing increased accuracy in positioning the sawblade 118. In some embodiments, accurate positioning of an orbit bracketis achieved using two shoulder screws 213 (see FIG. 11), or alignmentpins 214 (FIG. 12) which are received within corresponding bores (notshown) on the height adjust carriage 142. Alignment of the saw blade 118is further provided by incorporating an inner face 228 of the orbitbracket 203 with an angle 230 of about 0.65° with respect to a planeparallel to the drop plane (see below and FIG. 21). This angling of theinner face provides increased accuracy in positioning the saw blade 118throughout various beveling angles even when the belt 162 is underincreased tension.

Increased accuracy in positioning the blade 118 is further provided bythe manner in which the drop arm assembly 194 is movably connected tothe height adjust carriage 142. Specifically, as shown in FIG. 13, theorbit shaft 200 is movably supported within a drop arm frame 242 of thedrop arm assembly 194 by two bearings 215. A orbit bolt 232 threadedlyengages the orbit shaft 200 and compresses the bearings 215 against theinner bearing walls 234 of spaced apart brackets 236 of the drop armframe 242.

An orbit pin 216 extends through aligned bores 217, 218, and 219. Thebore 218 extends through the orbit shaft 200. The bore 217 extendsthrough an upper portion of the orbit bracket 203 while the bore 219extends through a lower portion of the orbit bracket 203. The orbitshaft 200 is thus rotatably fixed with respect to the orbit bracket 203.Two set screws 220 extend through bores 221 in the lower portion of theorbit bracket 203 and anchor the orbit shaft 200 against two shoulders222 of the orbit shaft bore 204 which are depicted in FIG. 14.

The shoulders 222 are formed in the orbit shaft bore 204 by forming alower circular portion 224 of the orbit shaft bore 204 and an uppercircular portion 226 of the orbit shaft bore 204. The lower circularportion 224 is substantially the same diameter as the diameter of theorbit shaft 200. The upper circular portion 226 in different embodimentshas the same or different diameter as the lower circular portion 224.The origin of the upper circular portion 226, however, is offset fromthe origin of the lower circular portion 224 in a direction opposite thelocation of the set screws 220.

Accordingly, the upper circular portion 226 provides sufficientclearance for a slip fit between the orbit shaft 200 and the orbit shaftbore 204. At the same time, the junction of the upper circular portion226 and the lower circular portion 224 form the shoulders 222 whichextend along the entire length of the orbit shaft bore 204.Consequently, when the set screws 220 are installed, the set screws 220force the orbit shaft 200 against the shoulders 222 forming a “threepoint” lock between each of the set screws and the shoulders.

In some embodiments, the shoulders are replaced by two ball bearingspressed into the drop arm frame 242 using the outer race of the bearing.The orbit shaft 200 is then inserted with one side of the orbit shaftengaging the inner race of one of the bearings. The orbit bolt is thenscrewed inside the orbit shaft from the opposite direction of the orbitshaft engaging the inner race of the other bearing. The orbit shaft andbolt assembly move the inner races of the two bearings towards eachother. With the outer races fixed in the drop arm, and the inner racespulled together, the internal clearances are minimized thus reducing oreliminating the side to side movement due to the internal clearances ofthe bearings.

Turning now to FIGS. 15A-C, the drop arm assembly 194 is depicted infurther detail. As noted above, the slave pulley 192 is engaged with thebelt 162 and rotatably supported by the drop arm assembly 194. Morespecifically, the slave pulley 192 is rotatably supported by an arborshaft 240 which is configured to rotatably support the blade 118 (seeFIG. 1). The arbor shaft 240 is rotatably supported within a drop armframe 242.

The drop arm frame 242 further includes a spring well 244 (FIG. 15B)which houses a spring 246. The spring 246 is operatively connected to aflange 248 of an arbor lock 250. The arbor lock 250 includes anactivation arm 252 positioned above the drop arm frame 242 and a lockingramp 254. The arbor 240 extends through an arbor slot 256 and twoshoulder screws 258 extend through guide slots 260 and threadedly engagethe drop arm frame 242.

The drop arm assembly 194 includes a capacitive coupling plate (CCP) 262from which extends a connector tab 264. The CCP is mounted to a CCPbracket 268 using screws, five screws either the same or different typesof screws 266 are illustrated, which in turn is mounted to the drop armframe 242 using three set screws 269. The CCP bracket 268 includes araised lip 270 configured to provide electrical isolation between CCPand the blade. While in the embodiment of FIG. 15a a single piece CCPbracket 268 is depicted, the bracket in other embodiments is formedusing multiple modules which in some embodiments are not connected toeach other.

The CCP 262 is part of a capacitive sensing system (discussed in furtherdetail below) and is made from electrically conductive material. As mostclearly depicted in FIG. 15C, the CCP 262 is not symmetrically shaped.Rather, the center of mass of the CCP 262 is shifted toward the orbiter272 of the drop arm frame 242. This shape provides sufficientcapacitance while reducing the inertia of the drop arm assembly 194. Inone embodiment, a finish treatment for the CCP 262 is a non-conductivecoating. Acceptable coatings include manganese phosphate for steel CCPsand anodizing for aluminum CCPs. Such thin non-conductive coveringsprovide isolation in case of accidental contact between the blade and aconductive portion of the CCP during heavy cuts due to blade deflection.

The CCP bracket 268 is made from a non-conductive material. In oneembodiment, a plastic with a low di-electric constant which is notaffected by water is used in order to minimize the capacitance variationin the system. The CCP bracket 268 is inserted into the drop arm andmanually adjusted to the proper distance from the blade then locked inplace by set screws 269 (see FIG. 15A, only two are shown).

Specifically, the screws 266 are used to mount the CCP 262 to the CCPbracket 268 by threadedly engaging protuberances 271. Optionally, afastening element such as a nut (not shown) in addition to the screws266 could be used to mount the CCP 262 to the CCP bracket 268. Inanother embodiment, the CCP bracket 268 is overmolded to the CCP 262 asa single unit. Thus, any fastening element is no longer required. Theprotuberances 271 are then inserted into wells 273 formed in the droparm frame and adjusted to set the CCP 262 at the desired location. Then,the set screws 269 are inserted through bores in the wells 273 to engagethe protuberances 271.

The protuberances 271 electrically isolate the screws 266 and the CCP262 from the drop arm frame 242. The raised lip 270 of the CCP bracket268 wraps around the CCP 262 along the outside edge to protect the CCP262 from incidental contact with the blade during heavy cutting.

Continuing with FIG. 15C, the orbiter 272 includes rebound ledges274/275 (see also FIG. 15A) and a pad 276 is mounted to a lower surfaceof the drop arm frame 242. As best viewed in FIG. 15B, the drop armassembly 194 further includes two alignment pins 278, a semi-sphericalstrike pin 280, and a latch pin 282 supported by the drop arm frame 242.

Referring now to FIG. 16, the drop arm assembly 194 is maintained in alatched position by a latch 300. The latch 300 is movably connected tothe pyrotechnic housing 322 by a pin 302. The latch 300, also shown inFIG. 17, includes a latch pin receiving area 304 which engages the latchpin 282 in the latched position. The latch 300 further includes twoprongs 306. The latch 300 is biased by a spring 308 such that the prongs306 are biased into contact with an actuator which in one embodiment isa shot 310.

The shot 310 is paired with another actuator or shot 312 by a cartridge314 shown in FIG. 18. A bridge 320 joins the two actuators or shots310/312 in the cartridge 314.

The cartridge 314 is shown in FIG. 17 mounted in a pyrotechnic housing322, also referred to as an actuator housing. The pyrotechnic oractuator housing 322, also shown in FIGS. 19-20, includes an internallythreaded chamber 324, a mounting plate 326, and a finger plate 328. Alocking ramp 364 is located at an upper portion of the finger plate 328.A slit 330 extends along one side of the internally threaded chamber 324and terminates at a rounded end portion 332. This configuration allowsfor optimal positioning of the active shot as explained with furtherreference to FIGS. 21 and 22.

FIG. 21 depicts a partial top plan view of the table saw 102 with thethroat plate 122 removed from a throat plate opening 334. Visiblethrough the throat plate opening 334 is an arbor nut 336 and the blade118 mounted to the arbor shaft 240. The drop arm 194 and a portion ofthe height adjust carriage 142 is also visible through the throat plateopening 334. Also depicted in FIG. 21 is a drop plane 338. The dropplane 338 is a plane that is aligned with where the shot 310 interfaceswith the drop arm assembly and along which the drop arm assembly movesin a substantially parallel manner when a saw control system isactivated as discussed more fully below. FIG. 22 depicts across-sectional view of the drop arm assembly 194 taken parallel to thedrop plane 338 of FIG. 21.

FIGS. 21 and 22, thus show that the drop arm assembly 194 is configuredsuch that the center of gravity 340 of the drop arm assembly 194 lieson, in proximity to or adjacent to the drop plane 338 so that thetransfer of force from the shot to the semi-spherical strike pin 280occurs as close as practicable to the drop plane 338.

Accordingly, the pyrotechnic housing 322 is configured to center theactive shot substantially on the drop plane 338. This results in reducedstress for the system and decreased drop time for the drop arm assembly194. Additionally, the inactive shot (shot 312 in the configuration ofFIG. 21) is positioned inwardly of the active shot while maintaining thecartridge 314 in a location which is easily accessible through thethroat plate opening 334. This configuration ensures that the inactiveshot does not interfere with the movement of the drop arm assembly 194.

To further improve the alignment of the active shot with thesemi-spherical strike pin 280, an alignment housing 342 is mounted tothe pyrotechnic housing 322 as shown in FIG. 17. The alignment housing342 receives the hardened steel alignment pins 278 (FIG. 15B) therebyreducing the blade deflection under load, as well as, ensuring properalignment between the active shot and the semi-spherical strike pin 280.Providing the pins 278 in the drop arm assembly 194 further providesenhanced stabilization of the drop arm frame 242 against side loading ortorsional loading against the orbit shaft 200 (FIG. 4). Using hardenedsteel pins as alignment pins extending from the aluminum drop arm frame242 achieves this benefit while allowing for a light weight/low inertiadrop arm frame 242.

While two pins 278 are shown in FIG. 15B, in other embodiments only oneis used. Yet in another embodiment, one or more protrusion or surfacesis used in the system. Additionally, in some embodiments the alignmenthousing is positioned in the drop arm assembly 194 while the hardenedsteel pins extend from the pyrotechnic housing 322. In furtherembodiments, the alignment features are integrated into the latch 300and/or the shots.

The slit 330 in the housing 322 receives the bridge 320 of the cartridge314. The slit 330 thus allows for a spare shot to be incorporated intothe cartridge 314. The slit 330, however, weakens the pyrotechnichousing 322. Consequently, support is required at both a forwardlylocation and a rearwardly location with respect to the slit 330 topreclude failure of the pyrotechnic housing 322. While the rearwardmounting plate 326 is firmly bolted to the height adjust carriage 142with two bolts 346 and a pin 348 shown in FIG. 23, bolting of theforward portion of the pyrotechnic housing 322 would result inunacceptably high stresses, even with the provision of the rounded endportion 332 which inhibits cracking at the end of the slit 330. It isfor this reason that the finger plate 328 is used.

As depicted in FIG. 17, the forward portion of the pyrotechnic housing322 is supported by contact between the finger plate 328 and fingerribbing 344 on the height adjust carriage 142. The finger plate 328 thustransfers force in the direction of the pyro firing (beneath thepyrotechnic housing 322), but does not constrain the pyrotechnic housing322 in any other degree of freedom, which greatly reduces the stresslevels in this part and allows the pyrotechnic housing 322 to be madefrom affordable and lightweight material. In this embodiment, threefingers are provided. In other embodiments, more or fewer fingers areprovided.

The disclosed pyrotechnic system provides a number of additionalfeatures. By way of example, the pyrotechnic assembly 350 of FIG. 24includes two shots 310/312. While the saw control system in someembodiments provides an electrical check to make sure that an unusedshot is connected, the safety control system in some embodiments is notconfigured to ensure that the connected shot is properly installed inthe pyrotechnic housing 322 and thus aligned with the semi-sphericalstrike pin 280. The pyrotechnic assembly 350 shown in FIG. 24, however,is configured to ensure that a user does not mistakenly connect thewrong shot.

FIG. 24 depicts the pyrotechnic assembly 350 which includes thepyrotechnic housing 322, the cartridge 314, and the shots 310/312 whichhave been described above. The pyrotechnic assembly 350 further includesan electrical connector 352, a connecting wire 354, and a reaction plug356.

Typically, the shots 310/312 and the cartridge 314 are provided as asingle unit. Additionally, the table saw 102 is provided with theconnecting wire 354 inserted through an opening 358 of the reaction plug356 as shown most clearly in FIG. 25. One end of the connecting wire 354is permanently attached to the saw control unit, while the other end isattached to the electrical connector 352.

The pyrotechnic assembly 350 is assembled by providing the shots 310/312in the cartridge 314. The shots 310/312 and the cartridge 314 are theninserted into the pyrotechnic housing 322. For a new unit, either shot310/312 is aligned with the housing axis 366 and inserted into theinternally threaded chamber 324. If the unit has previously been used,then the unused shot is inserted into the internally threaded chamber324.

Next, the electrical connector 352 is inserted into a plug of the shot310/312. The reaction plug 356 is then threaded into the internallythreaded chamber 324. Because the electrical connector 352 is largerthan the opening 358 (see FIG. 25), the reaction plug 356 can only bethreaded into the internally threaded chamber 324 if the electricalconnector 352 is connected to a shot located in the internally threadedchamber 324. The incorporation of the electrical connector 352 and amating connector on the shots thus enables the incorporation of amechanical/electrical lockout as described above.

In other embodiments, the reaction plug 356 and electrical connector 352can be replaced with a snap-on cap or a flashlight-like cap.Additionally, the electrical connector 352 can be omitted in suchembodiments and replaced with a simple pigtail connector.

The reaction plug 356 further assists in a lock-out function whichensures that the cartridge 314 is adequately seated within thepyrotechnic housing 322. As shown in FIG. 26, the spring 308 biases thelatch 300 in a clockwise direction. When the reaction plug 356 is notadequately threaded into the internally threaded chamber 324 as depictedin FIG. 26, the prongs 306 force the shot 312 upwardly within theinternally threaded chamber 324 and the latch 300 is rotated in aclockwise direction to a position whereat a lower surface of a lowerportion 360 of the latch 300 is located within the drop path of thelatch pin 282. Accordingly, counterclockwise orbiting of the drop armassembly 194 is constrained by contact between any portion of the droparm assembly and the lower portion 360. Consequently, the latch pin 282cannot be received within the latch pin receiving area 304.

By rotating the reaction plug 356 in a direction to further engage theinternally threaded chamber 324, the reaction plug 356 is forced againstthe cartridge 314 or the shot 310, forcing the shot 310 or the cartridge314 against the prongs 306. This forces the spring 308 into compression,and rotates the latch in a counterclockwise direction resulting in theconfiguration of FIG. 27. In FIG. 27, counterclockwise orbiting of thedrop arm assembly 194 is still constrained by contact between the latchpin 282 and the lower surface of the lower portion 360.

Continued rotation of the reaction plug 356 fully seats the cartridge314 within the internally threaded chamber 324, further rotating thelatch 300 to the configuration of FIG. 28. In FIG. 28, the latch 300 hasbeen rotated so that a side surface of the lower portion 360 is withinthe drop path of the latch pin 282. Accordingly, by orbiting the droparm assembly 194 in a counterclockwise direction, the latch pin 282presses against the side surface of the lower portion 360 furthercompressing the spring 308 and rotating the latch 300 in thecounterclockwise direction as the latch pin 282 slides upwardly alongthe side surface of the lower portion 360.

Continued counterclockwise orbiting of the drop arm assembly 194 movesthe latch pin 282 above the side surface of the lower portion 360.Accordingly, the spring 308 forces the latch 300 to rotate in aclockwise direction resulting in the configuration of FIG. 29. In FIG.29, the latch 300 has rotated in the clockwise direction such that thelatch pin 282 is received within the latch pin receiving area 304.

Accordingly, if the reaction plug 356 is not sufficiently threaded intothe pyrotechnic housing 322, the latch 300 provides a mechanical“lockout” and the drop arm assembly 194 cannot be raised into acutting/latched position. While described with respect to a pyrotechnicdevice, the reaction plug 356 can be used with actuators of any desiredtype to provide both mechanical and electrical lockout capabilities.

The reaction plug 356 is typically configured such that it can be easilyturned by hand. In one embodiment, the reaction plug 356 includes ribs362 (see FIG. 24) which are configured to allow fortightening/loosening. The ribs 362 are further configured to allow fortightening/loosening of the reaction plug 356 with a spanner wrench (notshown). In some embodiments, the reaction plug is a hex shaped plug thatcan be turned with a standard hex wrench instead of a spanner. Infurther embodiments, a locking feature separate from the reaction plugis provided which requires a tool to allow rotation of the reactionplug. By way of example, the locking feature may be a spring loadedcomponent (ball bearing, spring tab) which is operated by pushing on alocking tab that needs a screwdriver or similar tool to release. Inother embodiments, a hole and extruded pin with a circular reaction plugare used which require a special wrench to tighten and loosen thereaction plug.

The biasing of the latch 300 into the active shot by the spring 308 alsoassists in removal of the cartridge 314 as explained with initialreference to FIG. 30. FIG. 30 depicts the cartridge 314 fully seatedwithin the pyrotechnic housing 322. For removal of the cartridge 314,the reaction plug 356 is removed. Because the latch 300 is biasedagainst the active shot, removal of the reaction plug 356 allows thecartridge 314 to be pushed upwardly to the position depicted in FIG. 31.A user can then grasp the upper portion of the cartridge 314 above theinactive shot rather than pulling the cartridge 314 using the connectingwire 354.

Referring back to FIG. 16, when the active shot 310 is activated by asaw control system, the shot 310 applies force to the drop arm assembly194 through the semi-spherical strike pin 280 which is substantiallyaligned with the drop plane 338 by the housing 322. This force istransferred to the latch pin 282 (see FIG. 29) which forces the latch300 to compress the spring 308 and moves the latch pin receiving portion304 of the latch 300 out of the drop path of the latch pin 282. The droparm assembly 194 then orbits in a clockwise direction moving the blade118 (see FIG. 2) which is mounted to the arbor shaft 240 under theworkpiece support surface 104.

As discussed above, the location of the drop arm orbit axis 201 iscontrolled to be located between the axis of rotation 202 of the offsetdrive shaft 164 and an axis of rotation of the slave pulley 192. Thisarrangement provides for increased dropping speed of the drop armassembly 194 and prevents damage or stretching of the belt that wouldlead to degradation of powertrain performance as explained with furtherreference to FIGS. 6, 15A, and 32. FIG. 32 shows the drop arm orbit axis201, the axis of rotation 202 of the offset drive shaft 164, and theaxis of rotation 183 of the slave pulley 192. Since the pulley 166 ismounted to the height adjust carriage 142 and the slave pulley 192 ismounted on the drop arm assembly 194, tensioning of the belt 162 asdescribed above moves the pulley 166 away from the drop arm orbit axis201 (to the left in FIG. 32). As a result, during a drop arm drop theslave pulley 192 moves toward the pulley 166. Accordingly, the axis 183moves closer to the axis 202. This reduction in distance de-tensions thebelt which results in a faster drop time.

The impact of the drop arm assembly 194 is absorbed in part by contactbetween the pad 276 and a surface 374 as shown in FIG. 33. The pad 276is mounted on the drop arm assembly 194 using any desired mounting meanssuch as glue, fasteners, clamp plate, etc. Positioning the pad 276 onthe drop arm assembly 194 allows a pad with a smaller sized geometrythan mounting the pad on the surface 374.

For example, FIG. 33 depicts the location of impact between the drop armassembly 194 and the surface 374 when the height adjust carriage 142 isinitially in a fully raised position as depicted in FIG. 2. When theheight adjust carriage 142 is at a lowermost position as depicted inFIG. 34, the drop arm assembly 194 contacts the surface 374 at a lowerlocation as depicted in FIG. 35. Consequently, covering the span of thesurface 374 which is contacted by the drop arm assembly 194 would takemore material than is required to cover the portion of the drop armassembly 194 which contacts the surface 374. Consequently, mounting thepad 276 on the drop arm assembly 194 reduces the amount of pad materialthat is required.

The configuration of the drop arm frame 242 is thus selected in part toprovide the desired surface for contacting the surface 374. Returning toFIG. 22, the configuration of the drop arm frame 242 is further selectedto reduce the weight of the drop arm frame 242. As depicted in FIG. 22,a number of ribs 376/378/380/382 extend from a lower surface 384 to anopening 386 which receives the arbor shaft 240. The ribs 376/378/380/382provide strength which allows for less material to be used and/or forlighter materials to be used. In the context of the drop arm assembly194, this translates into a reduced moment of inertia thereby providinga more rapid lowering of the drop arm assembly in response to a sensedunsafe condition.

The ribs 376/378/380/382 also reduce the rebound force of the drop armassembly 194 once the pad 276 contacts the surface 374. As shown in FIG.22, the ribs 376/378/380/382 each define a respective axis388/390/392/394. The axes 388/390/392/394 intersect at a locus 396 whichcoincident with, adjacent to, in proximity to the center of gravity 340.This configuration reduces bounce-back energy and allows furtherreduction in the amount or weight of materials.

The above described configuration is typically insufficient fordissipation of all bounce back energy of the drop arm assembly 104.Accordingly, a bounce back latch assembly 400 is provided as shown inFIG. 36. The bounce back latch assembly 400 includes a lower latch 402and an upper latch 404 independently movably connected to the orbitbracket 203 by a pin 406. The pin 406 in some embodiments is sizedlonger than necessary to provide for tolerance. A wave washer (notshown) may be used between the head of the pin 406 and the latch 404 toallow for the tolerance while providing desired tension to the system.

The lower latch 402 and an upper latch 404 are biased into contact witha rebound surface 408 of the drop arm frame 242 by two springs 410 and412, respectively. The springs 410/412 are anchored to the orbit bracket203 by a bolt 414. The bounce back latch assembly 400 further includes areset lever 416 which extends from the lower latch 402 to a locationabove the orbit bracket 203.

During orbiting of the drop arm assembly 194 in response to a sensedunsafe condition, the rebound surface 408 orbits in a clockwisedirection (viewed as in FIG. 36). As the rebound surface 408 orbits, therebound ledge 275 (see FIG. 15A) orbits past the lower latch 402.Accordingly, the spring 410 biases the lower latch 402 into contact withthe rebound surface 408 at a location inwardly of the outermost extentof the rebound ledge 275. Subsequently, the drop arm assembly 194contacts the surface 374 as described above. When the drop arm assembly194 rebounds away from the surface 374, the lower latch 402 comes intocontact with the rebound ledge 275 precluding further upward(counterclockwise) movement of the drop arm assembly 194.

The rebound ledge 274 (see FIG. 15A) and the upper latch 404 operatesimilarly. The main difference is that for the rebound ledge 274 toorbit beneath the upper latch 404, more clockwise orbiting of therebound surface 408 is required. This occurs, for example, when theheight adjust carriage 142 is positioned toward its highest locationsuch as the height depicted in FIG. 16. Accordingly, at higherlocations, rebound protection is provided by the rebound ledge 274 andthe upper latch 404 while at lower heights, such as the height depictedin FIG. 34, rebound protection is provided by the rebound ledge 275 andthe lower latch 402.

When a user wishes to return the drop arm assembly 194 to a latchedposition, the user pushes against the reset lever 416 which moves thelower latch 402 away from the rebound surface 408. Additionally, a lip418 of the lower latch 402 contacts the upper latch 404, moving theupper latch 404 away from the rebound surface 408. The drop arm assembly194 can then be raised into a latched position held by the latch 300.

The above described use of ribbing to reduce the weight of the drop armassembly 194 also reduces the overall weight of the table saw 102,making the table saw 102 more portable. Ribbing is used in other areasof the table saw for the same purpose. For example, FIGS. 37-39 depictvarious views of the height adjust carriage 142. Extensive ribbing 420is provided in order to accommodate the large impact forces from theshots 310/312.

Similarly, the bevel carriage 134 includes ribbing 422/424/426/428 alongwith other structural features as depicted in FIGS. 40-41. Also shown inFIGS. 40-41 are openings 430 and 432. The ribbing 424 and 428 providesstructural support for the surface 374 which is impacted by the drop armassembly 194 as discussed above. The ribbing 422 and 426 and otherstructural features provide support which allows for the openings 430and 432 to be accommodated. The opening 430 is needed in order to allowfor mounting of the motor assembly 160 (FIG. 4) while the opening 432 isprovided to enhance operation of the saw control unit as will bediscussed in further detail below. In addition, the removal of thematerial to form the opening 432 reduces the weight of the saw.

Accordingly, in one embodiment ribbing is used throughout the table saw102 to keep the table saw 102 light and portable without compromisingstructure. Nonetheless, selective areas and components of the table saw102 are provided in the form of stronger materials to ensure optimalfunctioning of the table saw 102 even after multiple pyrotechnicactivations. For example, forces of the impact of a drop transferthrough the drop arm, orbit bracket and into the height adjust rods.Accordingly, the orbit bracket 203 (FIG. 10) and the area of thebevel/height adjust carriages around the height adjust rods aretypically formed with stronger and or heavier material. Likewise thealignment housing 342 (FIG. 17), the pyrotechnic housing, and the latch300 in some embodiments are made from stronger material such as by usingpowder metallurgy, zinc die-casting, or the like.

Because many of the structural components are formed of lightweightmaterial, forces from the pyrotechnics and from arresting the drop armassembly 194 are not damped. The transferred forces must therefore beaccounted for when positioning sensitive components. One such sensitivecomponent is housed within a saw control unit assembly 450 in FIG. 42which is mounted to the bevel carriage 134. The saw control unitassembly 450 includes electronics used to control the table saw assembly100. Such electronics include a memory with program instructions storedtherein which, when executed by a processor of the saw control unitassembly 450, controls the safety control system.

As shown in FIG. 43, the saw control unit assembly 450 includes aprinted circuit board (PCB) 452 which is mounted to an outer housing454. The outer housing 454 is in turn mounted to an inner housing 456.The saw control unit assembly 450 is then mounted to the bevel carriage134. The inner housing 456 and the outer housing 454 electricallyisolate the PCB 452 from the bevel carriage 134. A USB port 458 (seeFIG. 42) provides for electronic access to the PCB 452.

The foregoing configuration of the saw control unit assembly 450provides damping of the forces from the pyrotechnics and from arrestingthe drop arm assembly 194. Nonetheless, some of the forces may still betransferred to the PCB 452. Accordingly, if the PCB 452 is mountedperpendicular to either of these force vectors, a large impact/vibrationload will be applied to the PCB 452, which can cause damage to the PCB452. Accordingly, as best viewed in FIG. 44, the PCB 452 is mounted atabout a 15 degree angle with respect to the plane in which the forces ofthe shot and the impact on the surface 374 are applied.

If the PCB 452 is mounted in close proximity and parallel to aconductive body that is carrying a signal such as the bevel carriage asdiscussed in further detail below, the signal can be capacitivelycoupled to the PCB 452 and cause unwanted noise in other signals.Consequently, the bevel carriage 134 and the saw control unit assembly450 are configured such that there are no parallel metal surfaces tocouple noise to the PCB 452. It is for this reason that the opening 432is provided in the bevel carriage 134.

While the mounting of the PCB 452 on the bevel carriage 134 isconvenient for purpose of wire routing as discussed further below, insome embodiments the PCB 452 is mounted on a plastic base or undersideof the workpiece support surface. In these embodiments, the transfer offorce and signal coupling are reduced, but wire routing is typicallyless optimal. Mounting the PCB 452 to the underside of the workpiecesupport surface has the added advantage of using the workpiece supportsurface as a heat sink for heat generating components of the PCB 452such as a triac. In another embodiment, a component such as a second PCBthat generates heat other than the PCB 452 is mounted to the undersideof the workpiece support surface and uses the workpiece support surfaceas a heat sink.

As noted above, the positioning of the saw control unit assembly 450 isselected in one embodiment for the convenience of wire routing. Wirerouting for one embodiment is depicted in FIG. 45. In FIG. 45, the PCB452 is connected to the CCP 262 by a coaxial cable 460. The coaxialcable 460, shown in FIG. 46, includes a center conductor 462 which isinsulated from a shield 464 by an insulator 466. An outer plastic coat468 protects and insulates the shield 464. As shown most clearly in FIG.47, the center conductor 462 of the coaxial cable 460 is connected tothe connector tab 264 of the CCP 262 to provide a reliable connectionthat can withstand the shock loading of the pyrotechnic firing event.

Returning to FIG. 45, the coaxial cable 460 is connected to the heightadjust carriage 142 at location 470 and sufficient slack is provided inthe wire 460 between the location 470 and the connector tab 264 to allowfor the drop arm assembly 194 to move without detaching the coaxialcable 460 from the connector tab 264.

The coaxial cable 460 is further connected to the bevel carriage 134 atlocations 472 and 474 and the height adjust carriage 142 at location476. Sufficient slack is provided in the coaxial cable 460 between thelocations 474 and 476 to allow for movement of the height adjustcarriage 142 with respect to the bevel carriage 134.

At various locations the outer plastic coat 468 is stripped to exposethe shield 464. By way of example, FIG. 48 depicts a stripped area 478associated with the location 474. The stripped area 478 is placed indirect contact with the bevel carriage 134 at location 474. Typically, aprotective covering 480 (see FIG. 49) is then attached over the strippedarea 478 to protect the stripped area 478 and to ensure good contactbetween the shield 464 and the underlying metallic component.

Depending upon the location of the connection, a dual screw protectivecovering, such as the protective covering 480, or a single screwprotective covering such as the protective cover 482 of FIG. 50 may beused. One or more of the protective coverings in some embodiments areformed from a plastic, while in other embodiments one or more of theprotective covers are formed from metal to provide increasedconnectivity. Alternatively, the coaxial cable shield 464 can besoldered directly to other components or surfaces.

In some embodiments, only connection locations provided with aprotective cover 480/482 are stripped. Thus, in some embodiments thecable is stripped at the locations 472 and 476 of FIG. 45 but the cableis not stripped at the location 474.

The coaxial cable shield 464 is thus connected to metallic components insuch a way that the shield 464 can be connected to multiple pointswithout terminating, and also in such a way as to provide protection tothe coax cable 460 where the outer plastic coat 468 is stripped away.This ensures uninterrupted shield connection to all metal parts in theundercarriage assembly. The coaxial cable 460 is thus used to connectshield to the bevel carriage 134, height adjust carriage 142, the rivingknife 116 and associated components, etc.

Shield connection to the angle indicator 130 (FIG. 1) is also providedby the location 472. As discussed above, the location 472 is inelectrical communication with the bevel carriage 134, also shown in FIG.51. The bevel carriage 134 is in turn in electrical communication with abevel clamp 133. Finally, the bevel clamp 133 is pressed into electricalcommunication with the angle indicator 130 when the bevel carriage 134is locked by the bevel adjust lock 132. Thus, the angle indicator 130 isplaced in electrical communication with the shield 464.

The angle indicator 130 is electrically isolated from the workpiecesupport surface 108 by a non-conductive front plate 486. This allows theworkpiece support surface 108 to be maintained at “neutral” while theangle indicator 130 is at “shield”. In other embodiments electricalisolation is provided by plastic isolators as table connections, byusing an all plastic front plate or a plastic front plate with a smallinsert for bevel clamping, or by using an all metal front plate withnon-conductive isolators to the bevel lock and the workpiece supportsurface. If desired, the workpiece support surface 108 may be connectedto earth ground to reduce interference to the sensing system from staticelectricity. Static electricity from the blade and components connectedto shield can be ameliorated by connecting those components to earthground through a high resistance cable.

Because the bevel carriage 134 is suspended from the workpiece supportsurface 108, the support mechanisms must also be insulated. As shown inFIG. 52, the bevel carriage 134 includes a pair of beveling trunnions488 (only one is visible in FIG. 52) which are pivotably supported by apair of trunnion blocks 490 attached to the workpiece support surface108. The trunnion blocks 490 are insulated from the beveling trunnions488 by a pair of plastic trunnion inserts 492.

The angle indicator 130 is connected to shield in some embodiments,either alternatively or additionally, through the bevel carriage 134 orheight adjust carriage 142. By way of example, FIG. 45 shows the bevelcarriage 134 connected to “shield” at the locations 472 and 476.Electrical communication with the locations 472 and 476 may be providedthrough a powder metallurgy bracket 496 (see FIG. 51) in electricalcommunication with the height adjust rod 484 and/or through a threadedrod bracket 498 in electrical communication with the height adjust rod484. Thus, while the PM brackets 496/498 provide additional strengthwhich allows for other portions of the table saw 102 to be made withlightweight metals, they can also provide for good electricalcommunication between components.

As noted above, the height adjust carriage 142 is connected to theshield 464. The drop arm frame 242 is in turn in electricalcommunication with the height adjust carriage 142 through the orbitbracket 203. Accordingly, the arbor shaft 240 and blade 118 areelectrically isolated from the drop arm frame 242. As shown in FIG. 53,the arbor shaft 240 is electrically isolated from the drop arm frame 242by a plastic bearing housing 500 which houses a bearing 501 whichsupports a blade side 502 of the arbor shaft 240. A pulley side 504 ofthe arbor shaft 240 is supported by a bearing unit 506. The drop armframe 242 includes a plastic over-mold 508 which supports a back bearing510. Accordingly, the blade 118, as well as the arbor shaft 240, arbornut 336, and blade washers 512/514 are each electrically isolated fromthe drop arm frame 242. In an alternate embodiment, the bearing 510 isisolated by a component (not shown) wherein the component can beincorporated into the back bearing 510 either by pressed fit, adhesive,over-mold, or other techniques. The bearing can be made fromnon-conductive material such as ceramic material, as an example.

The arbor shaft 240 is further electrically isolated from the conductivebelt 162 (FIG. 15A) by the pulley 192. As depicted in FIGS. 53 and 54,the pulley 192 includes an inner core 520, an intermediate core 522, andan outer shell 524. A shim 526 is provided between the arbor shaft 240and an inner shim lip 528 of the slave pulley 192. In anotherembodiment, more than one shim may be used in the system. A jam nut 530maintains the pulley 192 on the arbor shaft 240.

The shim 526 provides the correct alignment between the pulley 192 andthe pulley 166. The motor end pulley 166 attaches to the motor assembly160. The driven pulley 192 is attached to the drop arm assembly 194.Because of the tolerance build up, it is possible for the two pulleys192/166 to be offset. Accordingly, in this embodiment one of the pulleysis fixed and the other is adjustable. While in the embodiment of FIG. 53a shim is used, in other embodiments the shim is replaced by a slidingcollar or a collar that can be adjusted by turning on an externalthread. Further embodiments incorporate an adjustable collar, a movablecollar with jack screw in the pulley, inclined planes on the pulley andshaft, a c-ring instead of the jam nut, an adjustable multi-piecepulley, or a method using differently sized pulleys based on actualshaft offset measurements.

Returning to FIG. 54, the inner core 520 is wear resistant and may bemade from a conductive material. The inner core 520 includes a bore 532configured to couple with the arbor shaft 240 such as by a threadedengagement. Other methods of engagement such as splined, a keyed, pressfit connection, or the like may also be used. The outer shell 524 isalso wear resistant and may be made from a conductive material. Theouter shell 524 includes an outer surface 534 configured to engage thebelt 162.

The intermediate core 522 is formed from a non-conductive material whichin one embodiment is an insert molded plastic. The outer surface 536 ofthe inner core 520 and the inner surface 538 of the outer shell 524include features to prevent slipping of the intermediate core 522 withrespect to the inner core 520 or the outer shell 524. The featuresinclude, but are not limited to, knurl, splined, dove-tail, protrudedstructure, anti-slip structure, locking structure, or the like.

As depicted in FIG. 54A, the outer shell 524 in this embodiment includessplines 540 which are dovetailed. The outer faces exhibit an angle 542of about 6°. This provides increased locking which is beneficial whenmaterials exhibiting different thermal expansion and contractioncharacteristics are used. Accordingly, when the intermediate core 522 isformed, complementary dovetail structures are formed in the intermediateshell as depicted in FIG. 54. Thus, the outer component and the innercomponent of the pulley define a plurality of dovetail connectionstherebetween.

In other embodiments, electrical isolation between the arbor shaft 240and the belt 162 is provided using an all plastic pulley, an anodizedaluminum pulley, or a plastic over-mold pulley.

In some embodiments, a non-conductive belt is used in place of theconductive belt 162. In this embodiment, a conductive pulley can be usedwith the non-conductive belt. In another embodiment, a conductive beltcan be used with one conductive pulley and one non-conductive pulley.

The motor assembly 160 shown in FIG. 6 is thus isolated from the arborshaft 240 by the pulley 192. As depicted in FIG. 6, the motor assembly160 is further isolated by the pulley 166 which is made like the pulley192 with a non-conductive intermediate core 580 between an inner core582 and an outer shell 584.

While the motor assembly 160 is thus electrically isolated from thearbor shaft 240 and blade 118, the motor is nonetheless capable ofgenerating electromagnetic interference. Accordingly, the motor assembly160 is configured to reduce the potential transmission of interferingelectromagnetic energy. As depicted in FIG. 6, the power shaft 168 isradially supported within a casing 586 by a bearing 588. The other endof the power shaft 168 is radially supported within the motor gearhousing 176 by a bearing 590. The offset drive shaft 164, containing thegear 170, is radially supported within the motor gear housing 176 by abearing 592. A bearing 594 is supported by a cover plate 596. The coverplate 596 is attached to the motor gear housing 176 and encloses thegear 170 and positions the gear 170 to be driven by an armature pinion.

If all of the foregoing components were made from metals, the motorassembly 160 would act like an antenna and transmit noise which couldinterfere with the sensing system. Specifically, the offset drive shaft164 (also called a gear shaft) and the bearings 588, 590, 592, and 594all transmit noise which if coupled to a large component like the motorgear housing 176, the motor casing 586, or the cover plate 596 would betransmitted in the vicinity of the sensing system if those componentswere made from metal. In order to reduce interference with the sensingsystem, the motor gear housing 176, the casing 586, and the cover plate596 are therefore made from plastic, significantly reducing the noisetransmitted by the motor assembly 160. In alternative embodiments, anon-metallic barrier is positioned between the shafts/bearings and thecover plate/gear housing.

In addition to interference from electrical noise, the motor assembly160 also generates carbon dust which can interfere with the operation ofthe sensing system including the CCP 262. For example, carbon dust fromuniversal motor brushes can build up on components and may form aconductive path that will affect the sensing system. Accordingly, unliketypical motor housings, the motor gear housing 176 is provided with anumber of radial air vents 610 as shown in FIG. 55. The radial air vents610 divert cooling air which is axially driven by a fan 612 (see FIG. 6)and divert the air radially. Accordingly, any carbon entrained withinthe fan driven air is forced in a direction away from electricallyisolated components including the CCP 262 thereby reducing thepossibility of carbon dust buildup between the isolated components.

In some embodiments, additional reductions in electrical noiseinterference are realized by incorporating an electronically commutatedmotor rather than an AC universal motor. An electronically commutatedmotor provides a more consistent noise level which is more easilymitigated and may reduce generated noise. Other noise reducing featuresinclude the incorporation of ceramic bearings instead of plastic bearingisolators, isolation of gear to pulley shaft with thermoset orthermoplastic, isolating the blade locally such as by usingnon-conductive blade washers, incorporation of non-conductive couplerson shaft, incorporating a partly non-conductive arbor shaft, or using analuminum gear housing with isolated bearings.

The fence 114 of FIG. 1 is also configured to reduce potentialinterference with the sensing system. Specifically, the fence 114 isremovably and movably attached to rails 620/622 which are mounted to theworkpiece support surface 108. The fence 114 is optionally in electricalcommunication with the workpiece support surface 108. Because the fence114 is movable, it is possible for the fence to come into contact withthe blade 118 or the riving knife 116 (or associated pawls). To reducethe potential for inadvertent contact which could affect the sensingsystem, the sides and top of the body portion of the fence 114 areformed with isolating components 624, 626, 628, respectively. Thisallows for internal components and end portions of the fence 114 to beformed from metal.

In one embodiment, one or more of the isolating components 624, 626, 628can be removed and reinstalled by the user to allow use of custom madejigs or fixtures with the tool. In another embodiment, a singleisolating component is used. The one isolating component may be “U”shaped to cover all three surfaces or simply cover one side of thefence.

In further embodiments, the body portion of the fence is over-moldedwith an isolation material. In some embodiments the riving knife andassociated pawls are isolated from the shield signal or formed fromnon-conductive materials. In some embodiments, the isolating component628 is omitted and kickback pawls are provided with a “lock-up” featuresimilar to those common with the overhead guard which lock up to preventcontact with the top of the fence. In further embodiments the isolatingcomponent 628 is omitted and the fence is configured to extend onlyacross the workpiece support surface 108 to a location at which itcannot contact the kickback pawls.

The throat plate 122 of FIG. 1 is also configured to reduce electricalinterference as explained with reference to FIG. 56. The throat plate122 includes an insert receiving area 640 in which an insert 642 ismounted. The throat plate 122 is configured to fit within the throatplate opening 334 in the upper surface of the workpiece support surface108. The throat plate 122 is removably mounted to the workpiece supportsurface 108 by first inserting two tabs 646/648 within slots (not shown)in the workpiece support surface 108 or under a lip (not shown) of theworkpiece support surface 108. A knob 650 is then rotated to lock thethroat plate 122 in place.

The knob 650 has a body portion 652 and a stem 654. The body portion 652is rotatably positioned in a knob well 656 in the workpiece supportsurface 108. The stem 654 extends through a hole (not shown) in the knobwell 656 to the underside of the workpiece support surface 108. A springassembly 658 is positioned on the stem 654 (see FIG. 57) beneath theworkpiece support surface 108 biasing the body portion 652 against thebottom of the knob well 656.

Turning to FIG. 58, the body portion 652 of the knob 650 includes twofinger holes 660, a locking cam 662 and a lifting cam 664. The fingerholes 660 provide an area for a user to gain leverage so as to rotatethe knob 650. In other embodiments, other geometry is provided to allowa user to gain leverage. In some embodiments, the body portion includesa coupling feature which allows a tool such as a screw driver, Allenwrench, or other tool to engage the knob 650 when rotation of the knob650 is desired.

The cams 662 and 664 selectively engage a cam ramp 666 located in a knobrecess 668 of the throat plate 122 shown in FIG. 59. By rotation of theknob 650 in a clockwise direction, the lifting cam 664 is rotatedbeneath the cam ramp 666 forcing the throat plate 122 upwardly so as toallow a user to more easily grip and remove the throat plate 122.Rotation of the knob 650 in a counter clockwise rotates the locking cam662 over the top of the cam ramp 666 thereby locking the throat plate inposition.

The knob 650 and the throat plate 122 in one embodiment are made ofplastic to preclude interference with the sensing system. In areas whichare subject to increased wear, metal inserts such as the insert 642 maybe used to provide increase wear resistance. Such metal inserts areinsulated from the workpiece support surface 108 by the plastic throatplate 122.

Removal of the throat plate 122 is typically desired in order tofacilitate changing of the blade 118 or other shaping device.Accordingly, a user simply rotates the knob 650 in a clockwise directionto force the throat plate 122 upwardly as described above and thenremoves the throat plate to expose the arbor nut 336 as depicted in FIG.21. Because the drop arm assembly 194 is supported solely by the latch300 (see FIG. 29), it may be possible for the user to dislodge the droparm assembly 194 inadvertently while loosening or tightening the arbornut 336. For example, when a blade wrench is used to turn the arbor nutin the tightening direction, a moment is generated which acts on thedrop arm orbiter 272 in a direction that acts against the supportingforce of the latch spring 308 and can cause de-latching. The arbor lock250 is used to preclude such de-latching as described below.

With reference to FIG. 15B, once the throat plate 122 is removed, a userpushes the activation arm 252 in the direction of the arrow 670.Referring now to FIG. 21, as the activation arm 252 is pushed in thedirection of the arrow 670 of FIG. 15B, the flange 248 compresses thespring 246 and the arbor lock 250 is forced in the direction of thearrow 672. The arbor lock 250 thus slides along the shoulder screws 258and the arbor shaft 240 by way of the guide slots 260 guided by theshoulder screws 258 and the arbor slot 256.

As the arbor lock 250 moves to the left as depicted in FIG. 15B, anarrow portion 674 of the arbor slot 256 moves into a notch 676 in thearbor shaft 240 locking the arbor shaft which allows a user to rotatethe arbor nut 336 (see FIG. 21).

Additionally, the locking ramp 254 is positioned onto the locking ramp364 as depicted in FIG. 60. Since the locking ramp 364 is a part of thepyrotechnic housing 332 which is mounted to the height adjust carriage142, the drop arm assembly 194 cannot be de-latched from the latch 300even while tightening the arbor nut 336. In alternate embodiments thearbor lock interfaces with other components attached to or a part of theheight adjust carriage 142.

Removal of the throat plate 122 further allows the user to reset thedrop arm assembly 194 in the event of de-latching of the drop armassembly 194 from the latch 300 either as a result of the saw controlunit or other de-latching. As shown in FIG. 61, the drop arm assembly194 may be reset by first pushing the reset lever 416 in the directionof the arrow 678 which moves the upper latch 404 and the lower latch402, as described above with respect to FIG. 36, allowing the drop armassembly 194 to be orbited upwardly. The user then positions a bladewrench 680 about the arbor nut 336 or the arbor shaft 240 to pull thedrop arm assembly 194 back into a latched position as described abovewith respect to FIGS. 26-29.

In some embodiments, a push stick or some other removable tool are usedto raise the drop arm assembly 194. In further embodiments, a hand holdis provided on the drop arm assembly itself. In still other embodiments,the drop arm assembly 194 is automatically raised such as by usingenergy stored during movement of the drop arm assembly 194 afterde-latching. In some of the embodiments, some of the energy frommovement of the drop arm assembly is stored in a spring positioned atthe surface 374.

The HMI unit 124 of FIG. 1 is shown in greater detail in FIG. 62. TheHMI unit 124 includes a housing 700, an access point 702, a near fieldcommunication (NFC) access point is illustrated herein, and a number ofstatus indicators 704. Other types of communication protocol such asBluetooth, zigbee, Wi-Fi, data protocol, mobile protocol, ultra wideband (UWB) protocol, or any frequency band are possible. The housing 700protects the other components of the HMI unit 124 while providing useraccess to components of the HMI unit 124. The NFC access point 702 is alocation at which an electronic device such as a smart phone can bepositioned in order to transfer data from a transceiver of the HMI unit124 to the smart phone. To this end, a user smart phone is provided withan application which includes communication protocols. A user can usethe NFC access point 702 to obtain current status of the table saw 102as well as unique identification information for the table saw. Theapplication can then be used to obtain maintenance recommendations,reset procedures or trouble-shooting procedures, and to provideregistration of the table saw. The application can further lock orunlock the system. For example, the application is used to lock orunlock one or more of the bypass switch and the motor power switch usinga personal identification number or code.

The status indicators 704 are used to provide desired alerts or statusindicators to a user. In some embodiments, the status indicators 704indicate power available, safety system in bypass, safety or systemerror which is correctable by the user, and safety or system error whichis correctable by a service center. In different embodiments, more orfewer status indicators 704 are provided. The construction of the HMIunit 124 enables viewing of the status indicators 704 even in brightsunlight as discussed with further reference to FIG. 63.

As shown in FIG. 63, the status indicators 704 are illuminated by fourLEDs 706 on a printed circuit board (PCB) 708. In some embodiments, theLEDS 706 are each provided as a colored LED having a color differentfrom the other of the LEDSs. An NFC antenna 710 is also provided on thePCB 708. The PCB 708 is supported by a support 712 which is attached tothe housing 700. A spacer 714 is attached to the support 712 by a numberof clips 716. The spacer 714 includes a number of wells 718 whichinclude openings (not shown) at a lower portion of the wells 718 whichreceive a respective one of the LEDs 706. The spacer 714 provides theproper spacing between LEDs and a diffuser 720, as well as the properspacing between the NFC antenna 710 and the smartphone access point 702.The wells 718 of the spacer 714 also prevent light bleed between thedifferent colored LEDs 706. The wells 718 of the spacer 714 furtherinclude one or more openings or passageways 719. The passageways channeldust away from the LEDs 706 thereby preventing the LEDs 706 from beingcovered.

The diffuser 720 includes a number of lenses 722, each lens associatedwith a respective one of the wells 718. The diffuser 720 retains LEDbrightness while diffusing light to look uniform across the exposedsurface. The diffuser 720 is made of material that is scratch andshatter resistant.

While some components of the table saw 102 are thus configured toprovide ease of access or use, access or use of some components by auser is not desired. By way of example, the PCB 452 must beelectronically accessible during assembly of the table saw 102 and insome instances by a service technician, but should not be accessed by auser. Accordingly, the USB port 458 is positioned to provide access to atechnician while limiting access to a user as discussed with initialreference to FIG. 64.

In FIG. 64, the table saw 102 is depicted with a zero bevel angle.Accordingly, a dust port 730 is positioned adjacent to a lower endportion of a dust port access slot 732 in the base housing 106. The dustport 730 is part of a dust shroud 734 which is attached to the bevelcarriage 134 (not visible in FIG. 64). In this position, neither theouter housing 454 nor the USB port 458 of FIG. 42 are visible to a user.

FIG. 65 depicts a rear view of the table saw 103 when the table saw 102is positioned at a forty-five degree bevel angle (the dust shroud 734 isnot depicted in this view). At this position, the outer housing 454 andthe USB port 458 are viewable through the dust port access slot 732.Accordingly, the USB port 458 is accessible by a service technician.Since a user is not expected to frequently look through the dust portaccess slot 732 at the angle depicted in FIG. 65, however, a user willgenerally not see the USB port 458. Accordingly, the USB port 458 isshielded from the user under most scenarios.

In some embodiments, access to the USB port 458 is further protectedsuch as by providing a protective plastic or rubber plug 736 (FIG. 66)or a cover 738 screwed down with tamper resistant screw 740 (FIG. 67).In some embodiments, the outer housing 454 must be removed to provideaccess to the PCB 452.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe disclosure are desired to be protected.

1. A power tool assembly comprising: a drop arm assembly movable along a drop path between a first drop arm assembly position whereat a portion of a shaping device supported by the drop arm assembly extends above a workpiece support surface and a second drop arm assembly position whereat the portion of the shaping device does not extend above the workpiece support surface, the drop arm assembly including a drop arm frame with an opening configured to rotatably support an arbor shaft, a lower surface spaced apart from the opening, and a plurality of ribs extending between the lower surface and the opening, wherein the plurality of ribs define a respective one of a plurality of axes, the plurality of axes intersect at a locus, and the locus is adjacent to, but spaced apart from, a center of gravity of the drop arm assembly; an actuating device configured to transfer a force to the drop arm assembly when the drop arm assembly is at the first drop arm assembly position; and a control system configured to control the actuating device to transfer the force to the drop arm assembly when an unsafe condition is sensed.
 2. The power tool assembly of claim 1, wherein; the drop arm assembly moves within a drop plane as it moves along the drop path; the center of gravity is at least in proximity to the drop plane; and the drop arm frame includes semi-spherical strike pin located in the strike plane.
 3. The power tool assembly of claim 2, wherein the drop arm frame is formed substantially from aluminum, the drop arm assembly further comprising at least one hardened steel pin extending from the drop arm frame; and the power tool assembly includes an alignment housing configured to receive the at least one hardened steel pin thereby aligning the semi-spherical strike pin with the actuating device.
 4. The power tool assembly of claim 2, further comprising: a stop pad mounted to the lower surface.
 5. The power tool assembly of claim 4, wherein the stop pad is positioned directly outwardly of at least two of the plurality of ribs.
 6. The power tool assembly of claim 3, wherein the plurality of ribs comprises at least four ribs.
 7. The power tool assembly of claim 3, wherein: the drop arm frame includes a pair of spaced apart brackets, each bracket including a respective inner bearing wall; an orbit shaft fixedly mounted to a height adjust carriage; a first bearing positioned about the orbit shaft and against a first of the respective inner bearing walls; a second bearing positioned about the orbit shaft and against a second of the respective inner bearing walls; an orbit bolt threadedly engaging the orbit shaft; and the orbit shaft and the orbit bolt are configured to compresses the first and second bearings against the respective inner bearing walls.
 8. The power tool assembly of claim 7, further comprising: a stop pad mounted to the lower surface.
 9. The power tool assembly of claim 8, wherein the stop pad is positioned directly outwardly of at least two of the plurality of ribs.
 10. The power tool assembly of claim 9, wherein the plurality of ribs comprises at least four ribs. 